Thomas McGrath, 15, of St. Henry District High School holds his model bridge after testing at the Balsawood Bridge Competition at Northern Kentucky University.

Written by

Kamellia Soenjoto Smith

His bridge looks like the Purple People Bridge that stretches from Cincinnati to Newport, except it's not purple and it's much, much smaller, about the size of a loaf of bread.

It weighs no more than a handful of leaves. That's because it's made from a very lightweight material, balsawood.

The tiny bridge is straddling two classroom tables and is connected to a contraption with a bucket hanging from it. The boy pours sand from a bowl into the bucket. The bridge begins to bend, but he keeps pouring. Lots of sand now, and then "Crack!" His bridge is broken. The bucket is lifted onto a scale and weighed - ...